Q.1 A piston-cylinder device contains 0.2 kg of air initially at 2.5 MPa and 350C. The air is first expanded isothermally to 600 kPa, then compressed polytropically with a polytropic exponent of 1.25 to the initial pressure, and finally compressed at the constant pressure to the initial state. Determine the boundary work for each process and the net work of the cycle. Q.2 A Carnot heat engine receives heat from reservoir at 850C at a rate of 750 kJ/min and rejects the waste heat to the ambient air at 25C. The entire work output of the heat engine is used to drive a refrigerator that removes heat from the refrigerator space at -5C and transfers it to the same ambient air at 25C. Determine (a) the maximum rate of heat removal from the refrigerated space and (b) the total rate of heat rejection to the ambient air Q.3 Refrigerant 134a enters the expansion valve of a refrigeration system at 1300 kPa as a saturated liquid and leaves at 240 kPa. Determine the temperature and internal energy changes across the valve. Q.4 A piston-cylinder device contains 0.8 kg of steam at 350C and 0.6 MPa. Steam is cooled at constant pressure until one-third of the mass condenses. (a) Show the process on both T-v and P-v diagrams (b) Find the final temperature (c) Determine the internal energy and volume change ZOOM +